Electrical rheostat



Oct. 11, 1955 c. G. PUCHY 2,720,570

ELECTRICAL RHEOSTAT Filed Feb. 4. 1955 2 Sheets-Shoot l IN V EN TOR.

CLARENCE G. PUCHY BY ATTORNEY Oct. 11, 1955 c. G. PUCHY ELECTRICAL RHEOSTAT 2 Shoets-$haet 2 Filed Feb. 4, 1955 ATTORNEY ELECTRICAL RHEOSTAT Clarence G. Puchy, Cleveland, Ohio, assignor to Jack &

Heintz, Inc, Cleveland, Ohio, a corporation of Delaware Application February 4, 1955, Serial No. 486,091

Claims. (Cl. 201-48) This invention relates in general to speed responsive control devices for electrical apparatus and more particularly to improvements in centrifugally responsive control devices employing a series of elements that are compressible together and whose resistance characteristics vary in accordance with the size of the air gaps therebetween.

I am aware of the state of the art as exemplified by such United States Letters Patent to Vacha, No. 2,460,246 of January 25, 1949, and 2,555,208 of May 25, 1951, which disclose a centrifugal speed governor including a rotary unit having a centrifugal weight and spring, a pressure responsive carbon pile resistor and a non-rotative spring acting on the resistor. The rotary unit has a centrifugally responsive spring to variably oppose the non-rotative spring in the running range of the electrical apparatus and means independent of the running range control for applying compressive pressure to the resistor under starting conditions. In addition, means are provided for bodily shifting the carbon pile resistance assembly axially between the two end supports.

The primary broad object of my invention is to provide a speed governor for electrical machines, such as direct current motors, inverters and the like, that will provide for smooth and efficient control without abrupt modulation of the output.

in accordance with the disclosures of the Vacha patents, supra, I likewise propose to employ a centrifugally responsive type of speed governor having a rotary unit having a spring and centrifugally responsive weights and a spring, a pressure responsive carbon pile resistor and a non-rotative spring acting on the resistor. The rotary unit has a spring variably opposing the stationary spring in the running range.

However, I have found objectionable the provision in these prior patented disclosures of means whereby the carbon pile resistor is supported for bodily shifting between its two end supports between the starting and running ranges. These carbon discs are mounted on an insulating spindle with no circumferential support. The bodily shifting of the resistor assembly creates undesired friction and this factor, coupled with the vibration of the machine in operation and the mounting of the carbon discs on the spindle, makes the resistance elements subject to breakage and dropping off of the supporting spindle.

I therefore propose to provide an assembly, and it is one of the primary objects of my invention to provide an assembly wherein, under idle condition, and in condition for starting the electrical apparatus, the centrifugal device effects proper contacts to the power source to start the device with the resistor shorted out during starting conditions. Only after running range is obtained does the centrifugally responsive spring of the rotary unit shift the contacts to bring the resistor into circuit with the power source. This entire cycle is obtained for idle, starting and running range without any bodily shifting of the tilted States Patent 0 resistor, and its attending friction factors and other disadvantages.

With the foregoing and other objects in view, the invention resides in the combination of parts and in the details of construction hereinafter set forth in the following specification and appended claims, certain embodiments thereof being illustrated in the accompanying drawings, in which:

Figure l is a view in vertical longitudinal section taken through a speed governor embodying the principles of my invention, showing the centrifugally responsive rotary unit in axially retracted position, opposing the non-rotative spring to effect proper contacts to bring the resistor into regulatory circuit with the speed governor during the running range;

Figure 2 is a similar but fragmentary view of the assembly under idle or starting conditions of the rotary unit wherein the centrifugally responsive spring is in axially extended position, permitting the grounded rod to be moved axially by the rotative spring and independentlyof the carbon pile stack, to effect proper contacts for a circuit from the power source through the rod for starting purposes, while shorting out the stacked resistor discs, which are not shifted in the process;

Figure 3 is a view in section taken along line 3-3 of Figure 1;

Figure 4 is a similar sectional view with the assembly nut removed; and

Figure 5 is a view in section taken along line 5-5 of Figure 1.

Referring more particularly to the drawings, I have shown in Figure l the non-rotative unit of the speed governor to include a rotary unit driven by the shaft 1 of the electrical machine and a non-rotative unit mounted in fixed position in the frame of the machine. The rotary unit is schematically shown as being driven by shaft 1 and has connected thereto a coil spring 2, to which is secured a flat spring 3 that is predeterminedly bowed to assume a normal position as shown in Figure 2, when the shaft 1 is at rest. The spring 3 has suitably secured thereto a pair of weights 4. The center of spring 3 has secured thereto a flat block 5. Upon the shaft gaining speed of rotation, the weights 4, being centrifugally responsive, partially straighten out the bow, and in doing so, shift block 5 axially to the right, as shown in Figure 1. Thus, the axial positions of the spring 3 and block 5 are dependent upon, and vary with the speed of rotation of the shaft.

The stationary unit is enclosed in a housing 6 provided with heat dissipating coiling radial fins 7. Disposed inside of an insulating tube 8 is a series of centrally apertured carbon discs to form a carbon pile resistor assembly 9. Mounted on the housing 6 in an insulating block 10 is a terminal post 11 provided with leads 12 in a cable 13 extending through a grommet 14 in a cover 15 to a suitable electrical power source. Also electrically connected to post 11 is a conductor plate 16 that extends angularly downwardly as a leg 16 to engage the right end carbon pile disc. To the right of leg 16' is an insulator ring 17. Disposed centrally through the stack of carbon discs 9, with appreciable radial clearance, is a conducting rod 18. The right end of rod 18 is enlarged and externally screw-threaded at 19 to receive a correspondingly internally screw-threaded end button 20 having a flange 21. A thin flexible centrally apertured diaphragm 22 is slipped over the end button 20 to abut the bottom flange 21 and the insulator block 17 where it is held by a screw plug 23 screwed into housing 6 and its central portion 24. This diaphragm functions as a centering spring support for the right end of rod 18. Fitted in the right side of rod 13 is a low friction material pin 25 which is in constant abutment with the rotatable plate of the rotary unit.

The left end of the housing is internally screw-threaded to receive an end member 26 and externally screw-threaded to receive a cover cap 27. The left end of rod 18 is externally screw-threaded to adjustably receive an end button 30 and between an internal shoulder of end member 26 and an external shoulder 31 of button 30, and surrounding button 30 is an expansive compression coil spring 32. Contacted by spring 32 and a snap ring 33 against the left side of button shoulder 31, and about the button 30, is a thin flexible diaphragm 33 that functions as a centering ring support for the button 30 and the left end of rod 18. A conductor washer 34 is interposed between button 30 and the left disc of the stack 9.

Figure 2 shows the assembly, including the rotary and non-rotary units, in position at rest and in position for starting. It will be seen that the bowed spring 3 and its fiat plate 5 in engagement with pin 25 of rod 18 is flexing the centering spring 22 to deform it and bring button 20 into electrical contact with leg 16 of the conductor plate 16 which is connected to the terminal post 11 and in circuit with the power source. The current thus flows from plate 16 through rod 18 to ground at the left end of the assembly. The carbon stack 9 is thus shorted out of circuit against the action of springs 22, 32 and 33.

This is of extreme importance because, as distinguished from the disclosures of the two Vacha patents, the presence of air gaps between the carbon pile discs is immaterial and, moreover, it is not necessary to compress them in order to properly effect the starting requirements.

Upon attainment of a predetermined speed of rotation of the shaft 1, the centrifugally responsive weights 4 cause the bowed spring to assume such a position as shown in Figure 1 in attempting to straighten out radially. The effect of this is to reduce the spring pressure on rod 18 to the left, permitting coil spring 32, with the assistance of flexed centering springs 22 and 33, to bodily shift the rod 18 to the right, as shown in Figure 1. This breaks the electrical contact between flange 21, of end button 20, and the leg 16 of contact plate 16, thus leaving rod 18 disconnected from the hot side of the power source. This does, however, place the carbon pile stack 9 in circuit with the power source through contact between leg 16 and the right end carbon disc. This occurs, of course, when the spring 32 is exerting a compressive force on the stack to variably reduce the air gaps between the carbon discs.

Neither operation calls for any bodily shift of the carbon pile stack whether from the idle, or starting, position of Figure 2, or the full running range of Figure 1, or any range therebetween.

It Will therefore be seen that I have provided a centrifugal type of speed governor which comprises a rotary unit having Weights and spring means, a pressure responsive carbon pile resistor, a non-rotative spring acting on the resistor, the rotary unit having spring means variably opposing the stationary spring in the running range control and a carbon pile resistor for obtaining low resistance under starting conditions, and in addition, I have obtained control means both for starting and running without bodily shifting axial movement of the carbon pile assembly, itself.

Regardless of whether my invention is embodied in a centrifugal type speed responsive governor, or other type of electrical apparatus, including a carbon pile type resistor, or whether the governor employs a rotary unit, I have provided actuating means adapted, under idle and starting conditions, for overpowering the non-rotative spring to short out the resistor and bring the rod into circuit with the hot side of the power source. Upon attaining running range, the non-rotative spring re-establishes the'resistor in the hot side of the source and var iablycompresses. the resistor.

I claim:

1. An electrical apparatus having a housing and in cluding a carbon pile resistor having a plurality of discs and means for supporting the same with their side surfaces adjacent each other, a rod extending, with radial clearance, through said resistor, an end button on each end of said rod and flexible means for axially floatingly suspending said end buttons and said rod, a power source and a conducting member in contact with one end of said resistor, the button adjacent the other end of said resistor having a spring adapted to shift the rod axially and to exert a compressive force upon the discs of the resistor, actuating means adapted under idle and starting conditions for overpowering said spring to force the adjacent end button into contact with said conducting member to short out said resistor and connect said power source to said rod and to ground said actuating means, when running range has been attained, being adapted to shift to permit said spring to exert an axial force on said rod to move the latter to break the contact between the opposite end button and said conductor member, compress said resistor discs and establish the resistor back in circuit with said power source, all without bodily shifting of said resistor.

2. An electrical apparatus having a housing and including a carbon pile resistor having a plurality of discs and means for supporting the same with the side surfaces adjacent each other, a rod extending, With radial clearance, through said resistor, an end button on each end of said rod and flexible means for axially floatingly suspending said end buttons and said rod, a power source and a conducting member in contact with one end of said resistor, the button adjacent the other end of said resistor having a spring adapted to shift the rod axially and to exert a compressive force upon the discs of the resistor, resilient actuating means under idle and starting conditions for overpowering said non-rotative spring to force the end button into contact with said conducting member to short out said resistor and connect said power source to said rod and to ground said actuating means, when running range has been attained, being adapted to shift to permit said spring to exert an axial force on said rod to move the latter to break the contact between the opposite end button and said conductor member, compress said resistor discs and establish the resistor back in circuit with said power source, all without bodily axial shifting of the resistor.

3. A speed responsive governor for regulating the speed of rotation of a shaft comprising a rotary unit carried by and driven by said shaft, said rotary unit having a centrifugally responsive member, and a non-rotative unit having a housing and including a carbon pile resistor having a plurality of discs and means for supporting the same with the side surfaces adjacent each other, a rod extending, with radial clearance, through said resistor, an end button on each end of said rod and a centering flexible diaphragm connecting each button to said housing for axially floatingly suspending said end buttons and said rod, a power sourceand a conducting ring in contact with the end of said resistor adjacent said rotary unit, the rotary unit centrifugally responsive member being in constant abutment with the adjacent end button of said rod, the other end button having a spring opposing the action of the centrifugally responsive member of the rotary unit to shift the rod axially and to exert a compressive force upon the discs of the resistor, said centrifugally responsive member, under idle and starting conditions, being able to overpower said spring to force the opposite end button into contact with said conducting ring to short out said resistor and connect said power source to said rod and to ground said centrifugally responsive member, when running range has been attained, being adapted to shift to permit said spring to exert an axial force on said rod to move the latter to break the contact between the opposite end button and said conductor ring, compress said resistor ring, compress said resistor discs and establish the resistor back in circuit with said power source, all without bodily axial shifting of the resistor.

4. A centrifugal governor comprising a rotary unit having a shaft driven bowed spring with a centrifugally responsive weight, and a non-rotative unit having a housing and including a carbon pile resistor having a plurality of discs and means for supporting the same with the side surfaces adjacent each other, a rod extending, with radial clearance, through said resistor, an end button on each end of said rod, a power source and a conducting ring in contact with the end of said resistor adjacent said rotary unit, the bowed spring having a member in constant spring urged abutment with the adjacent end button of said rod, the other end button having a spring opposing the action of the spring of the rotary unit to shift the rod axially and to exert a compressive force upon the discs of the resistor, said bowed spring under idle and starting conditions, being able to overpower said non-rotative spring to force the adjacent end button into contact with said conducting ring to short out said resistor and connect said power source to said rod and to ground, said weights, when running range has been attained, being adapted to expand said bowed spring radially to permit said nonrotative spring to break the contact between the opposite end button and said conductor ring, compress said resistor discs and establish the resistor back in circuit with said power source, all without bodily axial shifting of the resistor.

5. A centrifugal governor comprising a rotary unit of discs and means for supporting the same with the side surfaces adjacent each other, a rod extending, with radial clearance, through said resistor, an end button on each end of said rod and a centering flexible diaphragm connecting each button to said housing for axially floatingly suspending said end buttons and said rod, a power source and a conducting ring in contact with the end of said resistor adjacent said rotary unit, the bowed spring having a member in constant spring urged abutment with the adjacent end button of said rod, the other end button having a spring opposing the action of the spring of the rotary unit to shift the rod axially and to exert a compressive force upon the discs of the resistor, said bowed spring under idle and starting conditions, being able to overpower said non-rotative spring to force the adjacent end button into contact with said conducting ring to short out said resistor and connect said power source to said rod and to ground, said weights, when running range has been attained, being adapted to expand said bowed spring radially to permit said non-rotative spring to exert an axial force on said rod to move the latter to break the contact between the opposite end button and said conductor ring, compress said resistor discs and establish the resistor in circuit with said power source, all without bodily axial shifting of the resistor.

No references cited, 

